C3+ NGL Feed Preheater Flange Leak

[ghamsa]

Please help with the following.

PROCESS DESCRIPTION
There is ASME TEMA “R” DePropanizer Feed Preheater that uses 150 PSIG steam to increase C3+NGL stream from 65 F to 180 F with operating pressure of 350 PSIG on the shell side. The Preheater is made out of carbon steel. C3+NGL is on the Shell side while 150 PSIG steam is on the tube side.

One hour after the Preheater was depressurized, ice formed on the channel connection flange. Almost, 30 minuets later, minor hydrocarbon was coming out of the channel connection flange as the ice started melting.

My question:
Did the released hydrocarbon from flange indicate a damage gasket OR this hydrocarbon leak was expected during the depressurizing of this Preheater?

Thank you very much.

 

[quark]

Your gasket material seems to be incompatible with the temperature fluctuations. Evaporation of hydrocarbons may take place during depressurization and icing is formed as they pick up (part) heat of evaporation from the atmosphere. If the gasket can't take low temperatures it may become brittle and may leak afterwards. It is better to replace the gasket with a suitable one.

 

[ghamsa]

Thanks quark:

When maintenance tightened the bottles more land the leaks stop. The Preheater was back in service with no leaks with same gasket. Please note the gasket was in service for the past 3 years.

Also, could the hydrocarbon leak be attributed to gasket shrinkage?

Thx